linux-kernel - Re: 2.6.24-rc5-mm1: problems with cat /proc/kpageflags

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Message-Id: <200712161948.42656.m.kozlowski@tuxland.pl>
Date:	Sun, 16 Dec 2007 19:48:41 +0100
From:	Mariusz Kozlowski <m.kozlowski@...land.pl>
To:	Matt Mackall <mpm@...enic.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, sparclinux@...r.kernel.org,
	davem@...emloft.net
Subject: Re: 2.6.24-rc5-mm1: problems with cat /proc/kpageflags

> > >         cat /proc/kpageflags on sparc64 causes the box to lock.
> > > I can not write on any terminal - but I can issue sysrqs and switch
> > > between consoles.
> > > 
> > > cat process hangs in read(3, ...
> > 
> > cat /proc/kpagecount produces similar symptoms. box is locked - sysrq-w sshd trace:
> > 
> > __down
> > __down_interruptible
> > kobject_get
> > lock_kernel
> > chrdev_open
> > __dentry_open
> > nameidata_to_filp
> > open_pathname
> > do_sys_open
> > sparc32_open
> > linux_sparc_syscall32
> 
> Perhaps this is related to sparsemem.
> 
> Can you change line 710 of fs/proc/proc_misc.c to:
> 
> 	ppage = NULL;

Sure.

> ..and see if it still breaks?

Yes it does - the same way as eariler. Box is locked, processes stuck in D state
and after a while "BUG: soft lockup - CPU#0 stuck for 11s!".


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